Regression with kernel 4.20 on armhf

[Alex Deucher]

On Tue, Dec 18, 2018 at 8:58 AM Luís Mendes <luis.p.mendes at gmail.com> wrote:
>
> Hi Christian,
>
> I've been using a Sapphire RX 550 and a Sapphire RX 460 on a custom
> armhf board that runs well with Linux 4.19.9 at least, but now
> starting with Linux kernel 4.20, I'm having a gpu hang, right after
> the console being displayed, but before entering in graphical mode,
> when starting X session.
> I'm only reporting this now, because there was a PCI commit for mvebu
> that also entered for linux-4.20 that caused a kernel oops during
> pci_map_rom call in amdgpu initialization code. I've reverted that
> patch, but now amdgpu is hanging.

It would be useful if you could bisect.  This is the first I've heard
of amdgpu working on an ARM board without write combining (WC)
disabled.  You might check to see if disabling WC helps.  Return false
in drm_arch_can_wc_memory().

Alex

>
>
> [   24.801861] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring gfx
> timeout, signaled seq=2, emitted seq=3
>
> 02:00.0 VGA compatible controller: Advanced Micro Devices, Inc.
> [AMD/ATI] Baffin [Polaris11] (rev ff) (prog-if 00 [VGA controller])
>     Subsystem: Sapphire Technology Limited Baffin [Radeon RX 560]
>     Flags: bus master, fast devsel, latency 0, IRQ 51
>     Memory at d0000000 (64-bit, prefetchable) [size=256M]
>     Memory at e0000000 (64-bit, prefetchable) [size=2M]
>     I/O ports at 10000 [size=256]
>     Memory at e0200000 (32-bit, non-prefetchable) [size=256K]
>     Expansion ROM at e0240000 [disabled] [size=128K]
>     Capabilities: <access denied>
>     Kernel driver in use: amdgpu
>     Kernel modules: amdgpu
>
> dmesg follows in attachment.
>
> Regards,
> Luís
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